getgroups

, setgroups

- get or set supplementary group access list IDs

Synopsis

#include <unistd.h>
intgetgroups(intgidsetsize, gid_t *grouplist);

intsetgroups(intngroups, const gid_t *grouplist);

Description

The getgroups() function gets the current supplemental group access list of the
calling process and stores the result in the array of group IDs
specified by grouplist. This array has gidsetsize entries and must be large
enough to contain the entire list. This list cannot be larger than NGROUPS_MAX.
If gidsetsize equals 0, getgroups() will return the number of groups to
which the calling process belongs without modifying the array pointed to by
grouplist.

The setgroups() function sets the supplementary group access list of the calling
process from the array of group IDs specified by grouplist. The number
of entries is specified by ngroups and can not be greater than
NGROUPS_MAX.

Return Values

Upon successful completion, getgroups() returns the number of supplementary group IDs set
for the calling process and setgroups() returns 0. Otherwise, -1 is returned
and errno is set to indicate the error.

Errors

The getgroups() and setgroups() functions will fail if:

EFAULT

A referenced part of the array pointed to by grouplist is an illegal address.

The getgroups() function will fail if:

EINVAL

The value of gidsetsize is non-zero and less than the number of supplementary group IDs set for the calling process.

The setgroups() function will fail if:

EINVAL

The value of ngroups is greater than {NGROUPS_MAX}.

EPERM

The {PRIV_PROC_SETID} privilege is not asserted in the effective set of the calling process.

Usage

Use of the setgroups() function requires the {PRIV_PROC_SETID} privilege.